public class RecursionExercise02 {
    public static void main(String[] args) {
        CC cc = new CC();
        System.out.println(cc.eat(10));
    }
}

class CC{
    int num = 1;
    public int eat(int day) {
        if (day > 1) {
            num = (eat(day - 1) + 1) * 2;
        }
        return num;
    }
}